Practical Chiral Detectors
There are two basic types of chiral detectors for LC, those that measure optical rotation and those that measure circular dichroism. At the time of writing this book, the only commercially available chiral detectors are those that measure optical rotation. Nevertheless, a detector that measures circular dichroism and utilizes a diode array sensor system is thought to be in the design stage and will be briefly described later. The successful development of a chiral detector based on optical...
The Pulsed Discharge Electron Capture Detector
The pulsed discharge electron capture detector is an extension of the previously discussed pulsed discharge helium ionization detector, a diagram of which is shown in figure 19. The detector functions in exactly the same as that of the traditional electron capture detector but differs in the method of electron production. The Pulsed Discharge Electron Capture Detector Courtesy of Valco Instruments Company Inc. The Pulsed Discharge Electron Capture Detector Courtesy of Valco Instruments Company...
Low Dispersion Tubing
The dispersion that takes place in an open tube results from the parabolic velocity profile that occurs under conditions of Newtonian flow, i.e. when the velocity is significantly below that which produces turbulence. Under condition of Newtonian flow, the distribution of fluid velocity across the tube adopts a parabolic profile, the velocity at the walls being virtually zero and that at the center a maximum. This situation is depicted diagramatically in Figure 6A. Due to the relatively high...
Specific Derivatizing Methods
Specific derivatizing reagents take advantage of distinctive chemical characteristics of those solutes of interest and thus, generate colored or detectable derivatives of only those pertinent materials. Specific derivatization has two advantages firstly it only renders visible those solutes that are of interest and secondly, the solutes do not need to be completely separated from other materials that are of different chemical type because they will not appear in the separated mixture. Some...
The Nitrogen Phosphorus Detector NPD
The nitrogen phosphorus detector NPD sometimes called the thermionic detector is another sensitive, but, in this case, a specific detector, that is based on the FID. Physically the sensor appears to be similar to the FID but, in fact, operates on an entirely different principle. A diagram of an NPD detector is shown in figure 9. The essential change that differentiates the NPD sensor from that of the FID is a rubidium or cesium bead contained inside a heater coil close to the hydrogen flame....
The Thermal Argon Detector
Beres et al 6 showed that the argon detector could be made to function without a radioactive source or other electron producing device providing the argon and sensor system was operated at temperatures above 150 C. Glass becomes conducting at temperatures of 150 C and above, and so glass could be employed as one of the electrodes. A diagram of one form of the sensor is shown in figure 6. The argon from the column passes through a stainless steel tube, which acts as the anode, into a cylindrical...
Chromatographic Science Series
A Series of Monographs Editor JACK CAZES Cherry Hill, New Jersey 1. Dynamics of Chromatography, J. Calvin Giddings 2. Gas Chromatographic Analysis of Drugs and Pesticides, Benjamin J. Gudzinowicz 3. Principles of Adsorption Chromatography The Separation of Nonionic Organic Compounds, Lloyd 4. Multicomponent Chromatography Theory of Interference, Friedrich Helfferich and Gerhard Klein 5. Quantitative Analysis by Gas Chromatography, Josef Novak 6. High-Speed Liquid Chromatography, Peter M....
Argon Detectors Helium Detectors and the Electron Capture Detector Introduction
Around the late 1950s and early 1960s, Lovelock 1 developed a family of four detectors, starting with the argon ionization detector and ending with the electron capture detector 2 . The first of the family was called the macro argon detector for reasons that will shortly become apparent and although it is rarely used in GC today, it will be briefly described, as it is an extremely sensitive detector and its function has a bearing on that of the electron capture detector, which is a very...
The Multi Wavelength Fluorescence Detector
The multi wavelength fluorescence detector consists of two monochromators, the first that selects the wavelength of the excitation light and the second disperses the fluorescent light and provides a fluorescence spectrum or allows the separation to be monitored at a selected fluorescence wavelength, A diagram of the multi wavelength fluorescence detector is shown in figure 4. Basically the detector comprises a fluorescent spectrometer fitted with suitable absorption cell that can be used with...
The MultiElectrode Array Detector
The effective use of an electrode array as a liquid chromatography detector is largely possible due to the development of the porous carbon electrode. This electrode is made of porous graphitic carbon, which has a very high surface area, is mechanically robust and, more important, is permeable to the mobile phase. As a consequence, flow through electrodes can be constructed. The material commends itself to electrochemical detection in a number of ways. As the surface area is greatly in excess...
The Evaporative Light Scattering Detector
The evaporative light scattering detector incorporates a spray system that continuously atomizes the column eluent into small droplets that are allowed to evaporate, leaving the solutes as fine particulate matter suspended in the atomizing gas. The atomizing gas may be air or an inert gas if so desired. The suspended particulate matter passes through a light beam and the light scattered by the particles viewed at 45 to the light beam using a pair of optical fibers. The scattered light entering...